Energy traders are also waiting for Friday's Rig Count data from Baker Hughes for further clues on whether American shale producers keep returning online, as crude prices stabilize. Last week, the US oil rig count surged by 9 to 337 for the week closing June 10. It was the third straight weekly soar.

Initial results in Britain’s referendum on membership of the EU shook the financial markets as the “Remain” camp seems to be losing.

The shock arose after a devastating victory for Leave in Sunderland, northeastern England. Only City of Newcastle voted to stay in the European Union.

The outcome appeared to be stronger for Leave than pundits had actually expected. However, they might be just an early indicator of divergent regional voting patterns.